1. Field of the Invention
The present invention generally relates to the testing of devices on a substrate, such as semiconductor chips on a wafer, and more particularly, the present invention relates to a test probe apparatus and method which include a mechanism for determining when cleaning of probe needles is necessary.
A claim of priority under 35 U.S.C. § 119 is made to Korean Patent Application No. 2003-0006022 filed on Jan. 29, 2003, the entire contents of which are hereby incorporated by reference.
2. Description of Related Art
The manufacture of semiconductor devices generally involves a fabrication process in which a wafer is patterned into a plurality of chips, and an assembly process in which the chips patterned on the wafer are divided into individual unit chips. In addition, between these processes, an electric die sorting (EDS) process is performed to test the electrical characteristics of each of the chips of the wafer. The EDS process is used to identify any defective chips of the wafer.
The EDS process typically employs a test apparatus which applies an electrical signal to the chips of a wafer, and detects defective chips by examining a signal returned from the chips on the wafer. The electrical signals are applied to the chips using a probe card having probe needles which contact electrode pads of the wafer.
As the contact frequency of the probe needles with the electrode pads of the wafer is increased, metal substances (for example, aluminum oxides) of the electrode pads tend to stick to the probe needles. This increases the contact resistance of the probe needles, which in turn deteriorates the reliability and yield of the test process.
Therefore, a cleaning process is conventionally used to remove residues present on the probe needles. Typically, an abrasive member in the shape of a wafer removes the residues by polishing. One such structure is disclosed in Japanese Patent Disclosure Pyoung No. 11-87438 (entitled by “CLEANING MEMBER OF PROBE LEADING EDGE, CLEANING METHOD, AND TESTING METHOD OF SEMICONDUCTOR WAFER”). Here, a cleaning member is configured by a polishing layer made of elastic resin and abrasives, and a substance removal film bonded to a surface of the polishing layer. During cleaning, the tip of the probe needle pierces the removal film and is polished by the polishing layer, and then substances stuck to the tip are removed by the removal film when the probe needle is extracted.
In the conventional apparatus, a cleaning process is performed on the probe needles in a predetermined cycle. For example, the cleaning process may be routinely performed after the testing of each set of five wafers.
One drawback of cyclical cleaning is that the cleaning is often performed before is it actually necessary. Since the abrasive used in the cleaning process results in wear on the probe needles, excessive cleaning reduces the expected life span of the probe needles.
Another cleaning apparatus is disclosed in Japanese Patent Disclosure Pyoung No. 2002-26090 (entitled by “WAFER HOLDER OF WAFER PROBING APPARATUS”). This apparatus is characterized by the provision of at least one spray nozzle placed on a wafer holder which ejects a three-state material in which solid, liquid, and gas states exist together. The probe needles of a probe card are cleaned by the spray. The apparatus, which includes a controller for controlling the spray and a controller unit for controlling the controller, is advantageous in that it avoids the use of an abrasive and thus increases the life span of the probe needles. However, the structure is highly complicated, and there is no mechanism for determining exactly when cleaning is necessary.